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%I #13 May 19 2024 21:55:18
%S 2,5,7,55,70,188,248,273,385,416,479,530,574,892,1833,4057,4299,6188,
%T 14699,21121,88293,89608,95776,162620,196881
%N Numbers k such that 3*10^k - 59 is prime.
%C For k > 1, numbers k such that the digit 2 followed by k-2 occurrences of the digit 9 followed by the digits 41 is prime (see Example section).
%C a(26) > 2*10^5.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 29w41</a>.
%e 2 is in this sequence because (3*10^2 - 59)/3 = 241 is prime.
%e Initial terms and associated primes:
%e a(1) = 2, 241;
%e a(2) = 5, 299941;
%e a(3) = 7, 29999941;
%e a(4) = 55, 29999999999999999999999999999999999999999999999999999941; etc.
%t Select[Range[2, 100000], PrimeQ[(3*10^# - 59)/3] &]
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more,hard
%O 1,1
%A _Robert Price_, Oct 12 2017
%E a(24)-a(25) from _Robert Price_, Sep 08 2018